In current provider networks, a connection can be established and provided to a client. The client can use this connection in his client network and transmit data traffic over the connection. An important aspect is resilience. Several options exist to react on a network failure in the provider network which affects the connection.
A first option is what is known as protection. This means that in advance of any failure, a second redundant connection is established in the provider network between the provider edge nodes, which can then autonomously switch over in the case of a failure from the failed connection to the redundant connection. This will typically occur in less than 50 ms. Protection, however, is an expensive premium service that reserves bandwidth, which will be unused during normal operation, and that has to be booked by the client at an extra charge.
Another possibility is known as network restoration. After occurrence of a failure, a restoration path is determined in the provider network and the failed connection is then re-established over the restoration path. This network restoration can happen automatically through the network management system of the provider or, in case of an automatically switched (optical) network, through a distributed control plane of the provider network. Network restoration takes typically longer than protection to recover the traffic from the failure. The network restoration capability is also a feature that has to be booked by the client in advance, which is typically done in a service level agreement (SLA) between the provider and the client. Restoration mechanisms are known for example from US5435003 and WO97/50211.
A third alternative would be that the client himself provides in his client network sufficient spare capacity, which allows him to recover from a failure without involving the network provider by rerouting the failed traffic over his own spare resources. This alternative may be advantageous for large client networks, since it may save fees charged by the provider for protection or restoration services.
Finally, a fourth variant would be that the client requests from the network provider as a reaction to a failure a new connection and reroutes in his client network traffic from the failed connection over the new connection once established to recover from the failure. In this bandwidth on demand scenario, however, source and sink of the new connection cannot be planned in advance and therefore, the network provider is not able to efficiently plan his network. Moreover, after repair of the failure, the network provider is not able to modify automatically the on-demand connection to revert to the situation before the failure.